Simulation of Three-Leg VSC based Dstatcom for Power Quality Improvement

The distribution systems are facing severe power quality problems due to the large number of three phase and single phase linear, non-linear loads. These loads may be supplied from three-phase ac mains with neutral conductor. This creates excessive neutral current, high reactive power and harmonic current burden, load unbalancing, poor voltage regulation, etc. A three-phase fourwire distribution static compensator (DSTATCOM) based on a T-connected transformer and three leg voltage source converter (VSC) is proposed for power quality improvement. The T-connected transformer mitigates the excessive neutral current, and the IGBT based 3 leg VSC with a dc capacitor compensates the harmonic current, reactive power and balances the load. The Synchronous Reference Frame Theory (SRFT) based control scheme is proposed to extract reference currents and generates gate pulses for IGBT switches by hysteresis PWM technique. In this paper SRFT control algorithm is implemented by using PI and Fuzzy controllers. The performance of the proposed SRFT based three-phase four-wire DSTATCOM is implemented using MATLAB/SIMULINK. From the simulation results, it is observed that Fuzzy controller gives better performance than PI controller.